Tension machine



Aug, 7, 1956 A. P. HELDENBRAND TENSION MACHINE 4 Shets-Sheet 1 Filed April 1, 1955 INVENTOR. Arthui" P Helo/enbrand ATTORNEY.

Aug. 7, 1956 A. P. HELDENBRAND 2,757,536

TENSION MACHINE Filed April 1, 1955 4 Sheets-Sheet s 66 V @IP 971,

55 mow INVENTOR. Arthur I? #:s/dsulzrana/ ATTORNEY.

TENSION MACHINE Arthur P. I-Ieldeubrand, Oklahoma City, Okla.

Continuation of abandoned application Serial No. 229,106, May 31, 1951. This application April 1, 1955, Serial No. 498,576

3 Claims. (Cl. 73-97) This invention relates to improvements in machines of the type used to straighten and tensile test elongated elements, such as oil well pump rods and tubing. This is a continuation of my co-pending application entitled Devices For Straightening And Testing Oil Well Pump Rods, Serial No. 229,106, filed in the United States Patent Oflice on May 31, 1951, now abandoned.

As it is well known in the oil industry, a large portion of the present day oil wells are artificially produced by a rod-type pump. The pump is installed in a tubing at the bottom of the oil well and is actuated by a string of sucker rods extending upwardly through the tubing to a surface power unit. During operation, the rods are reciprocated to actuate the pump, and frequently rub against the tubing-causing wear of the rods. Also, the rods are repeatedly stressed and frequently become Weak.

The pump is periodically removed from the well for inspection and replacements of pump rings and the like. As the rods are pulled, they usually are visually inspected for wear. However, the rods can be, and frequently are, weak or worn, but the condition can not be determined by a visual inspection. Therefore, the rods are re-run in the well in a weakened condition, and sometimes break or part during operation of the pumping unit; thereby resulting in an expensive fishing job to recover the pump, as well as a substantial loss of operating time. Some of the rods removed from the well may also be bent, and it straightened by present equipment, will be weakened to such an extent that they will very likely break during subsequent use.

The present invention contemplates a novel machine for tensioning such rods for simultaneously straightening the rods and testing the tensile strength of the rods. The machine grips the ends of the rod (preferably the threaded end portions of the rod) and stretches the rod to its calculated tensile strength. If the rod withstands the desired pull, it will be straightened from end-to-end and will be of suflicient strength to provide a continued pumping operation without breaking. If the rod is not of sutlicient strength to withstand the desired tension, the machine will either pull it apart or stretch it to such an extent that the operator of the machine will observe its weakened condition. In either of the latter events, the rod will be discarded and not re-run in the well.

The present invention also contemplates a machine of the above character which can be made portable, whereby it can be positioned near the well for tensioning the rods at the well site. Furthermore, the machine maybe suspended in the well derrick to test the rods as they are pulled from the well.

An important object of this invention is to provide a novel machine for tensioning elongated elements, whereby the elements are simultaneously straightened and tested for tensile strength.

Another object is to provide a means for'testing and straightening sucker rods at the well site.

Another object of this invention is to tensile test elongated elements throughout their length.

nited States Patent ice A further object of this invention is to test the strength of the threads at each end of an elongated element, as well as the main body portion of the element.

A still. further object of this invention is to provide a simply constructed tensioning machine which may be economically manufactured.

Other objects and advantages of the invention will be evident from the following detailed description, when read in conjunction with the accompanying drawings, which illustrate my invention.

In the drawings:

Figure 1 is a plan view of my novel tensioning machine having a sucker rod secured therein.

Figure 2 is a side elevational view of the machine.

Figure 3 is an enlarged plan view of the front (the left end of Figures land 2) of the machine.

Figure 4 is a side elevational view of the portion of the machine shown in Figure 3.

Figure .5 is a sectional view as taken along lines V-V of Figure 4.

Figure 6 is another sectional view as taken along lines VI-VI of Figure 3.

Figure 7 is a schematic drawing of the hydraulic system utilized in my machine.

Figure 8 is a vertical sectional view through one control valve assembly of the hydraulic system.

Figure 9 is a vertical sectional view through another control valve, with portions of the valve assembly shown in elevation.

Figure .10 is a view taken at rightangles to Figure 9 and illustrating the operation of the valve assembly.

Figure 11 is a detailed sectional View through the rear end of the machine.

Figure 12 is a longitudinal sectional view through the opposite endsof the machine showing the use of modified clamps.

Figure 13 is a typical end elevational view of the structure shown inFigure 12.

Referring to the drawings in detail, and particularly Figure 1, it will .be observed that the machine has a centrally located, substantially square supporting frame F comprising a pair of side members 17 and 18 connected by a front cross member 19 and a rear cross member 20. A pair of leaf springs 21 '(see Figure 2) are secured under the side members 17 and 18 and extend under a transversely extending axle 23. A saddle strap 24 (Figure 2) secures each of the springs 21 to the axle 23, and the opposite ends of the springs are pivotally secured by brackets 26 and bolts 27 to the supporting frame F in the usual manner. Suitable wheels 28 and 29 are rotatably secured on the opposite ends of the axle 23.

A channel member 30 is rigidly secured on the sup porting frame at right angles to the axle 23 and extends forwardly from the "front cross member 19, as well as rearwardly from the rear cross member 20. The legs of the channel 30 are turned upwardly, whereby the channel receives and supports an elongated tubular member 31 therein. The tube 31 is preferably rigidly secured in the channel 30 by any suitable means, such as welding.

The rearend of the tube 31 (the right: end as shown in Figures 1 and 2) has a sleeve or collar 32 rigidly secured thereon to receive :an extension element 33. It will be observed in Figure 11 that theelement 33 is telescoped into the outer end of the sleeve 32 into contact with the outer end of the tube 31 and forms an extension of the tube 31-. Various lengths of extension elements .33 are preferably provided to vary the effective length of the tube 31 for purposes as will the more fully hereinafter set forth. An iamiular shaped head 34, having an outwardly extending shoulder 34a, is fitted in the outer end of the extension element .33 with the shoulder 34a in contact withthe end of the element 33. A pair of slips 35 and 35a extend into the head 34 to engage one end portion of the sucker rod 36 which is to be tensioned. The inner bore 34b of the head 34 may be tapered to facilitate the wedging action of the slips 35 and 35a.

The opposite or forward end of the tube 31 has a stretcher tube 37 slidingly telescoped thereover, as shown more clearly in Figures 3-6. An annular shaped head 38, resembling the previously described head 34, is secured in the outer end of the tube 37 to receive slips 39 and 39a, whereby the opposite end of the sucker rod 36 may be engaged. It will be apparent that the rod 36 extends through the supporting tubes 31 and 37, and will be placed under tension when the tube 37 is moved forwardly over the tube 31, or to the left as shown in Figures 1-5. The tube 37 is moved on the tube 31 by a hydraulic system and assembly as will now be described.

A pair of hydraulic cylinders 40 and 40a (shown best in Figures 3-5) are secured in parallel relation on opposite sides of the tube 31 by a pair of spaced brackets 41 and 42. It will be observed that the cylinders 40 and 40a are not only parallel to one another, but are also parallel to the tube 31, and are rigidly secured to the tube 31. A pair of pistons 43 and 43a are reciprocally disposed in the cylinders 40 and 40a respectively. The piston 43 has a piston rod 44 which extends through the forward end of the cylinder 40. And the opposite piston 43a has a piston rod 44a extending through the forward end of the respective cylinder 40a.

The piston rods 44 and 44a are connected to the stretcher tube 37, preferably by cars or plates 45, 45a, 46 and 46a (Figure 6). The ears 45 and 45a are rigidly secured to one side of the tube 37 in vertically spaced relation to extend outwardly above and below the piston rod 44. Mating apertures 48 (Figure are formed through the rod 44 and ears 45 and 45a to receive a vertically extending pin 47 (Figure 6) for completing the connection of the rod 44 to the tube 37. The ears 46 and 46a are secured in a similar manner to the opposite side of the tube 37 above and below the other piston rod 44a. Also, apertures 48 are provided in the rod 44a and the ears 46 and 46a to receive similar securing pins 471;. It will thus be apparent that the piston rods 44 and 44a are adequately secured to the stretcher tube 37 to move the tube 37 forwardly over the tube 31 when the pistons 43 and 43a are moved forwardly in the cylinders 40 and 40a.

The hydraulic system just described is utilized only for moving the tube 37 in one direction, that is, forwardly or in a direction to exert tension on the sucker rod 36. In order to retract the tube 37, or move the tube 37 onto the tube 31, I prefer to utilize a plurality of tension springs 49 through 490 (Figures 3-6). A ring 50 is secured around the tube 37 near the outer end thereof by suitable screws 51 to receive the forward ends of the springs. The opposite ends of the springs are secured to the forward cylinder bracket 41. As shown in Figure 6, the springs 49 through 49c are arranged in equally spaced relation around the tube 37 to provide a substantially straight retracting pull on the tube 37, to slide the tube 37 onto the tube 31 and retract the pistons 43 and 43a in the cylinders 40 and 40a.

As shown in Figures 1 and 2, the machine has a hydraulic fluid supply tank 52 mounted on the supporting frame F to supply fluid to a pair of pumps 53 and 54. The pump 53 is preferably a low pressure, high speed pump; whereas, the pump 54 is a high pressure, low speed pump, for supplying fluid to the cylinders 40 and 40a in variable amounts, as will be hereinafter set forth. Both of the pumps 53 and 54 may be of the hand operated type, wherein the pump 53 has a handle 53a and the pump 54 has a handle 54a. In regulating the pressure and flow of the hydraulic systems, I utilize a pair of novel control valves 55 and 56, a pressure guage 57 and a suitable check valve 59 (Figure 7).

The control valve 56 (the valve used for relieving the pressure of the hydraulic system) is shown in detail in Figures 9 and 10, and comprises a cylindrical housing 56a secured on top of the tube 31 by a bracket 60. A pair of vertically spaced couplings 61 and 62 project from one side of the housing 56a to provide a fluid inlet at the lower end of the housing and an outlet at the upper end of the housing as will be more fully hereinafter set forth. A valve plate 63, having a sealing ring 64 on the lower end thereof, is reciprocally disposed in the housing 56a. The valve plate 63 normally rests on an inwardly projecting seat 64a to separate the upper portion X of the housing 56a from the lower portion Y. A valve operating rod 65 depends from the lower face of the valve plate 63 and extends loosely through the seat 64a. The rod 65 extends on downwardly through a suitable packing gland 66 at the lower end of the housing 56a and terminates a substantial distance below the housing 56a, yet above the tube 31.

A suitable wing nut 67 is secured on the lower end of the rod 65 to limit the relative downward movement of a ring or collar 63. The ring 68 is slidingly disposed on the rod 65 and has a pair of upwardly extending toggle links 69 and 69a pivotally secured on opposite sides thereof by pins 70 and 70a respectively. A second pair of toggle links 71 are pivotally secured to the upper ends of the links 69 and 69a by pins 73 and 73a. As shown most clearly in Figure 10, a U-shaped handle 72 extends downwardly and outwardly from the lower ends of the links 71 for manual operation of the valve 56 as will be more fully hereinafter set forth. The links 71 extend on upwardly into proximity with the lower end of the housing 56a and have outwardly extending pins 74 and 74a in the upper ends thereof. The pins 74 and 74a pivotally secure the upper ends of the links 71 to a pair of brackets 75 and 75a depending from the housing 56a.

It will thus be apparent that when the centrally located pins 73 and 730 are moved forward (to the left as shown in Figure 10), the upper links 71 will be pivoted clockwise, and the lower links 69 and 690 will be pivoted counter-clockwise. Also, since the upper ends of the links 71 are secured in a fixed vertical position, the lower links 69 and 69a will be moved a short distance upward to raise the ring 68 on the rod 65 above the nut 67. The rod 65 and valve plate 63 can then move upwardly (as will be hereinafter described) until the valve plate 63 reaches the dotted line position 63a as shown in Figure 10.

A slide 76 having a slot 77 therein extends loosely over the pin 73 and has a stop member 78 adjustably secured thereon by a set screw 79 for contacting and actuating the pin 73. The slide 76 extends substantially horizon tally and is pivotally secured at its forward end by a pin 80 to an actuating or pull rod 81. As shown in Figure 4, the pull rod 81 extends forwardly over the tubes 31 and 37 and through the other control valve assembly 55. A helical tension spring 811 is disposed on the central portion of the rod 81 and is anchored to the rod 31 at one end by a flange 81b. The opposite end of the spring 81a is anchored to a bracket 81c extending up wardly from the tube 31. Therefore, the spring 810 constantly urges the rod 81 rearwardly to retain the slide stop 78 (Figure 10) out of contact with the pin 73.

The valve assembly 55 contains a pair of clutch jaws 82 and 83 arranged below and above the pull rod 81 as shown in Figure 8. The lower clutch jaw 82 is rigidly secured to a U-shaped bracket 84 depending from the valve housing 55a. Brackets 85 are bolted to the bracket 84 and stretcher tube 37 to rigidly support the valve assembly 55 on the tube 37 and provide movement of the valve assembly 55 with the tube 37.

A piston 86 is reciprocally disposed in the housing 551/: and has a valve stem 87 depending from the lower face thereof. The stem 87 extends through the lower end 551? of the housing 55a and supports the upper clutch jaw 83 above the pull rod 81 and lower jaw 82. A sleeve 88, having turning cars 89 and 90, is telescoped over the stern 87 and threaded into the lower end 55b of the housing 55a to retain a helical spring. 91 against the lower face of the piston 86. The spring 91 extends around the stem 87 and contacts the lower end of the piston to constantly urge the piston 86 upwardly. It will be apparent that the position of the threaded sleeve 88 determines the upward force exerted by the spring 91.

Downward movement of the piston 86 is also resisted by retaining devices secured in the walls of the housing 55a. Each retaining device comprises a ball 92 disposed in the inner end of a cup 93 which extends through the wall of the housing 55a and is secured to the housing in any suitable manner. The outer end of each cup 93 is closed and each cup contains a small compression spring 94 constantly urging the respective ball 92 inwardly. A circumferential groove 95 is preferably provided in the outer periphery of the piston 86 to receive the balls 92.

Fluid is supplied to the upper end of the housing 55a through a coupling 55c. It will be apparent that when a suflicient pressure occurs in the chamber Z above the piston 86 to overcome the action of the retaining devices, the balls 92 will be forced outwardly into the cups 93, and the piston 86 will be forced downwardly with a snap action. The upper clutch jaw 83 then contacts the pull rod 81 and the rod is gripped between the jaws 82 and 83. As long as the jaws 82 and 83 grip the rod 81, the rod will move simultaneously with the stretcher tube 37. The spring 91 also resists the pressure in the chamber Z, but when the balls 92 are retracted, the spring 91 gives way and the piston 86 will descend with a quick, snap action.

The above described hydraulic units or assemblies are interconnected by piping as diagrammatically illustrated in Figure 7. A suction pipe 96 extends from the supply tank 52 to the inlets of the pumps 53 and 54. The discharge from the pumps 53 and 54 is directed through branch lines 97a and 97b into a common header 97. As indicated in the drawing, the check valve 59 is interposed in the branch line 97a and prevents the high pressure from the pump 54 from reaching the low pressure pump 53 and causing damage to the low pressure pump. The pipe 97 communicates with a pipe 98 leading to the hydraulic cylinders 48 and 40a, as well as the control valve 55. That portion of the conduit 98 leading to the valve 55 is preferably flexible and is secured in the coupling 55c (Figure 8) to permit movement of the valve 55 with the stretcher tube 37. The pressure guage 57 communicates with the conduit 98 through a small conduit 99 to indicate the pressure in the cylinders 40 and 40a.

A conduit 166 interconnects the suction pipe 96 to the upper coupling 61 (Figure 10) of the pressure relieving control valve 56. Another conduit 100a interconnects the conduit 98 (Figure 7) to the lower coupling 62 (Figure 10) of the control valve 56. Therefore, the conduits 100 and 100a and valve 56 form a bypass around the pumps 53 and 54 to relieve the pressure in the cylinders 48 and 4% as will be hereinafter described.

My tensioning machine is also provided with suitable ront and rear stabilizing devices 104 and 1.10 (Fig. 2) to retain the machine in a substantially horizontal posi tion during operation. However, the stabilizing devices or supports 18 i and 110 should be retractable (not shown) to facilitate movement of the machine on the wheels 28 and 29. Also, I provide a pulling eye 121 secured to the rear end portion of the tube 31 by a pad 122 to facilitate pulling the machine on the wheels 28 and 29.

Operation The heads 34 and 38 (Figures 1, 2 and 11), along with the extension 33 and the slip jaws, are removed and one of the sucker rods 36 is inserted lengthwise through the tube 31 and stretcher tube 37. The head 38 is preferably first telescoped over the respective end of the rod 36 and placed in the end of the stretcher tube 37, and the slip jaws 39 and 39a are inserted. in the head :38 as shown in Figure 2. The rod 36 is then manually pulled to the rear (to the right as shown in Figures 1 and 2) until the shoulder 36a of the rod. 36 is. engaged by the slip jaws 39 and 39a. An extension element 33 of proper length is then telescoped over the opposite end of the rod 36 and inserted in the coupling 32. The outer end of the element 33 should be in proximity with, but slightly inward of, the adjacent end of the rod 36. The head 34 is then telescoped over the rod 36 and placed in the end of the extension 33, and the jaws 35 and 35a are inserted in the head 34' as shown in Figures 1, 2 and 11. The jaws.35 and 35a should be positioned inwardly of the rod shoulder 36b in order that they will engage the shoulder 36b when the tubes 37 and 31 are extended as will be hereinafter set forth.

Upon installation of the sucker rod 36, the large pump 53 (Figures 1 and 2) is operated by rocking the handle 53a to the supply fluid H under pressure to the main cylinders 40 and 40a in large quantities. The large pump 53 is used first, since it will supply a larger quantity of fluid than the pump 54 to initially extend the tubes 31 and 37 and bring the slip jaws 35 and 350 into engagement with the shoulder 36b in a fast and efficient manner. When the hydraulic pressure begins to increase and the pump 53 becomes hard to pump, the high pressure pump 54 may be placed in operationto complete the tensioning of the rod 36.

Referring to Figure 7, it will be observed that the fluid pumped by the high pressure pump 54 flows through the conduits 97b, 97 and 98 into the cylinders 40 and 40a. Since the only difference between the flow paths of the fluid discharged. by the pumps 53 and 54 is in the branch lines 97a and 97b, only the function of the high pressure pump 54 will be described unless otherwise indicated. In each operation, the fluid is directed to the cylinders 49 and 40a to act on the pistons 43 and 43a (Figures 3-6) respectively, and move the pistons forwardly. The movement of the pistons 43 and 43a is transmitted through the piston rods 44 and 44a, pins 47 and 47a and ears 45, 45a, 46 and 46a to the stretcher tube 37. Since both of the cylinders 4t) and 46a are subjected to the same fluid pressure, the pistons 43 and 43a will be moved uniformly to move the stretcher tube 37 to the rear in a direction away from the tube 31. Therefore, the heads 34 and 38 (Figures 1 and 2) will be moved in relatively opposite directions to exert a tension on the sucker rod 36 through the jaws 35 and 35a and shoulder 36b at one end and the jaws 39 and 39a and shoulder 36a at the opposite end.

Simultaneously with the exertion of fluid pressure in the cylinders 46 and 4011, the fluid is supplied through the nozzle 550 (Figure 8) to the control valve 55, as well as through conduit 100a and coupling 62 (Figure 10) to the lower chamber Y of the control valve 56. The fluid pressure is also transmitted through the conduit 99 (Figure 7) to the pressure gauge 57 whereby the operator will be advised of the amount of pressure being. exerted.

The valve 63 (Figures 9 and 10) will be retained on the seat 64a to close off the conduit 100a from the conduit 100 until the fluid pressure reaches a predetermined point as will be hereinafter described. Also, the retaining device 92.-94 (Figure 8) and the spring 91 will retain the piston 86 in its upper position to maintain the clutch jaws 82 and 83 open until the designated pressure is reached.

When the desired maximum tension has been placed on the rod 36, the pressure in the chamber Z (Figure 8) of the control valve 55 overcomes the action of the retaining spring 94 and the compression spring 91. The balls 92 will then be forced out of the groove 95 and the piston 86 will he forced downwardly with a snap action to close the jaws 82 and 83 on the pull rod 81. A continued movement of the stretcher tube 37 moves the pull rod forwardly and brings the slide stop 78 (Figure 10) into contact with the pin 73. The toggle links 69, 69a and 71 are thereby moved out of alignment to raise the ring 68 (Figure 9) on the valve stem 65. The fluid pressure in the chamber Y of the control valve 56 then moves the valve 63 upwardly to the dotted line position 63a andprovides communication between the conduits 100a and 100.

Referring to Figure 7, it will then be apparent that the pressure in the cylinders 40 and 40a will be bled-off through the conduits 98 and 100a, control valve 56, and conduits 100 and 96 back to the supply tank 52. As the pressure in the cylinders 40 and 40a is relieved, the large springs 49 through 490 (Figure 4) pull on the ring 5'3 to retract the stretcher tube 37 onto the tube 31 as well as move the pistons 43 and 43a into the cylinders 40 and 40a. The heads 34 and 38 (Figures 1 and 2) can then. be removed and the rod 36 moved lengthwise out of the tubes 31 and 37. The rod 36 will then be straight and of the desired tensile strength for re-use.

Also, when the pressure of the hydraulic system is released, the spring 91 (Figure 8) raises the piston 36 to the position shown and disengages the clutch jaws i2 and 33 from the pull rod 81. The spring 81a (Figure 4) then moves the pull rod 81 rearwardly to its normal operating position. And the valve 63 (Figure as well as the toggle links 69, 69a and 71, assume their normal positions as shown in solid lines.

As previously indicated, the spring 91 (Figure 8) can be adjusted by the sleeve 88 and determines the force required to actuate the piston 86. Therefore, the spring 91 controls the maximum pressure of the hydraulic system and the amount of tension exerted on the sucker rod 36. Inasmuch as the desired tensile strength of the rod 36 will be known, the maximum pull and hydraulic pressure can be easily determined. The spring 91 is adjusted to permit a downward movement of the piston 86 when this pressure has been reached. The operator will learn the desired settings for the sleeve 88 and spring 91 with experience. In any event, if the pressure gauge 57 indicates that the pressure of the hydraulic system is getting too high, the operator can move the handle '72 (Figure 10) up to the dotted line position 72a. The valve 63 will then move upwardly and relieve the hydraulic pressure as described above. The handle 72 may also be used in the event the rod 36 does not have the desired tensile strength and breaks during the tensioning operation.

In many instances the coupling portions of a rod 36 outwardly of the shoulders 36a and 36b (Figure 1) will be bent out of alignment with the remainder of the rod, or the slip jaws 35, 35a, 39 and 39a will grip the shoulders 36a and 36b unevenly to bend the extreme ends of the rod. To alleviate this condition, I have provided the novel clamping device shown in Figures 12 and 13. Some rods have pins 36X or boxes 36Y on each end and some have a pin 36X on one end and a box 36Y on the opposite end. My device can be adapted for either pins or boxes, therefore, I have shown one end of the rod 36 with a pin 36X and the opposite end with a box 36Y.

This clamping device comprises a plate or flange 130 having a shaft 131 extending from one face thereof. The shaft 131 is of a size to be inserted through either of the heads 34 or 38 and the flange 130 will abut the outer face of the respective head to align the shaft 131 with the center line of the head. An arm 132 is secured across the outer face of each flange 130 by screws or the like 133 and has an outwardly extending handle 134 on one end thereof.

The inner end of the shaft 131 is threaded, and when used on a box 36Y, it can be threaded directly into the box. When used for engaging a pin 36X, an adapter 135, having internal threads in each end thereof, is used. The adapter 135 is threaded onto the pin 36X and then the shaft 131 is threaded into the opposite end of the adapter by turning the handle 134.

When the tube 37 is moved outwardly on the tube 31, the heads 34 and 38 will engage the flanges 130 to align the shafts 131 with the tubes 31 and 37. Therefore, when an outward force is applied on the heads 34 and 38, the coupling portions of the rod 36 will be aligned and straightened with the remainder of the rod. Also, the threads at each end of the rod 36 will be tested for strength along with the main body portion of the rod.

From the foregoing it is apparent that the present invention provides a novel machine for tensioning elongated elements, whereby the elements will be simultaneously straightened and tested for tensile strength. The elements will be straightened and tested throughout their entire length, and the operation can be conveniently carried out at the well site to preclude the necessity of transporting the elements. Furthermore, the elements can be stress aligned to actually increase their strength as well being straightened and tested. Also, the threads, as well as the main body portions of the elements, will be tested. In addition, it will be apparent that the present invention provides a simply constructed tensioning machine which may be economically manufactured.

Although the foregoing description has related to the straightening and testing of sucker rods, it will be understood by those skilled in the art, that the present invention may also be utilized for tensioning substantially any large elongated elements, such as oil well tubing and drill pipe. The invention is particularly useful for tensioning elongated elements having threaded ends.

Changes may be made in the combination and arrangement of parts as heretofore set forth in the specification and shown in the drawings, it being understood that any modification in the precise embodiment of the invention may be made within the scope of the following claims without departing from the spirit of the invention.

I claim: 4

1. In a machine for tensioning an elongated element having threaded ends, comprising a pair of heads, each of said heads having a bore therethrough and a flat surface on the outer face thereof at right angles to said bore, a support retaining said heads in spaced relation with said bores in aligned relation, at least one of said heads being movable on said support, a clamping member for each of said heads of a size to extend through the bore of the respective head for threadedly engaging one end of the elongated element, each of said clamping members having an outwardly extending flange of a size to contact the flat surface of the respective head when said member is inserted in the bore of the respective head, and power team for moving said heads in relatively opposite directions over said clamping members with said flat surfaces into contact with said flanges, whereby tension is applied on the elongated member throughout the length thereof.

2. In a machine for tensioning an elongated element having threaded ends, comprising a pair of heads, each of said heads having a bore therethrough and a flat surface on the outer face thereof at right angles to said here, guides retaining said heads in spaced and aligned relation, at least one of said heads being movable on said guides, a clamping member for each of said heads of a size to extend through the respective head for threadedly engaging one end of the elongated element, each of said clamping members having an outwardly extending flange of a size to contact the flat surface of the respective head around the respective bore, a hydraulic system connected to said heads for moving said heads in relatively opposite directions over said clamping members to contact said flanges and apply tension on the element, and control means for relieving the hydraulic system upon the application of a predetermined tension on the element.

3. In a machine for tensioning an elongated element having threaded ends, comprising a hydraulic cylinder, a clamping member carried by said cylinder for threadedly engaging one end of the element, a piston reciprocably disposed in said cylinder, a piston rod on said piston extending through one end of said cylinder, a second clamping member carried by said piston rod for threadedly engaging the opposite end of the element and applying tension on the element upon movement of said piston in one direction, a pump for supplying fluid under pressure to said cylinder and moving said piston in said one direction, a toggle operated relief valve carried by said cylinder, 21 control valve carried by said piston rod and arranged to operate in response to a predetermined pressure in said cylinder, clutch jaws carried by said control valve and movable upon operation of said control valve, and a pull rod secured to said toggle operated valve and extending through said clutch jaws, whereby operation of said control valve actuates said clutch jaws into engagement with said pull rod for operating said toggle relief valve in 10 response to movement of said piston after a predetermined pressure is reached in said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,303,621 Donnelly -l Dec. 1, 1942 2,363,930 Basquin Nov. 28, 1944 2,375,032 Parke May 1, 1945 2,708,363 Nass May 17, 1955 

